Fatty acid analogues for the treatment of cancer

ABSTRACT

The present invention relates to fatty acid analogues of general formula (I): R 1 -[x i -CH 2 ] n —COOR 2 , wherein is: a C 1 -C 24  alkene with one or more double bonds and/or with one or more triple bonds; and/or a C 1 -C 24  alkyne, and/or a C 1 -C 24  alkyl, or an alkyl substituted in one or several positions with one or more compounds selected from the group comprising fluoride, chloride, hydroxy, C 1 -C 4  alkoxy, C 1 -C 4  alkylthio, C 2 -C 5  acyloxy or C 1 -C 4  alkyl, and wherein R 2  represents hydrogen or C 1 -C 4  alkyl, and wherein is an integer from 1 to 12, and wherein i is an odd number and indicates the position relative to COOR 2 , and wherein X i  independent of each other are selected from the group comprising O, S, SO, SO 2 , Se and CH 2 , and with the proviso that at least one of the X i  is not CH 2 , which can be used for the treatment and/or prevention of primary and secondary metastatic neoplasms.

[0001] The present invention relates to fatty acid analogues which canbe used for the treatment and/or prevention of cancer. Morespecifically, the invention relates to the use of the fatty acidanalogues for the treatment and/or inhibition of primary and secondaryneoplasms.

BACKGROUND OF THE INVENTION

[0002] Treatment with modified fatty acids of the present inventionrepresents a new way to treat these diseases.

[0003] EP 345.038 describes the use of non-β-oxidizable fatty acidanalogues for the treatment of hyperlipidaemic conditions and forreducing the concentration of cholesterol and triglycerides in the bloodof mammals.

[0004] PCT/NO95/00195 describes alkyl-S—CH₂COOR and alkyl-Se—CH₂COOR forthe inhibition of the oxidative modification of LDL, and for thereduction of the proliferation of cancer cells. However thisproliferative effect is cell spesific, and we have shown that thecompounds of the present invention in other cell systems have no effecton cell growth or proliferation.

[0005] PCT/NO99/00135, 00136 and 00149 describe the use of the fattyacid analogues for the treatment of obesity, diabetes and stenosis.

[0006] It has now been found that the analogues described in the priorart publications mentioned above, i.e. the non-β-oxidizable fatty acidsin accordance with the present invention have broader area ofapplications. We have shown that the compounds of the present inventioninhibit the growth and metastatic behaviour of tumours, and increase theoverall survival of animals with implanted tumours.

CANCER

[0007] The development of new and more effective chemotherapeutic agentsfor cancer treatment requires consideration of a variety of factorsincluding cytotoxicity, tumour cell proliferation, invasion andmetastasis. Conventional anticancer agents have typically beenidentified on the basis of their cytotoxicity alone.

[0008] Tumour progression is thought to occur when variant cells havingselective growth properties arise within a tumour cell population, andone of the final stages of tumour progression is the appearance of themetastatic phenotype. During metastasis, the tumour cells invade theblood vessels, survive against circulating host immune defences, andthen extravasate, implant, and grow at sites distant from the primarytumour. This ability of tumour cells to invade neighbouring tissues andto colonise other organs is among the leading causes of cancer relateddeaths.

[0009] The term metastasis encompasses a number of phenotypic traitswhich together result in the clinical problem that most often leads todeath from cancer. The cells lose their adherence and restrainedposition within an organised tissue, move into adjacent sites, developthe capacity both to invade and to egress from blood vessels, and becomecapable of proliferating in unnatural locations or environments. Thesechanges in growth patterns are accompanied by an accumulation ofbiochemical alterations which have the capacity to promote themetastatic process.

[0010] So far, little is known about the intrinsic mechanism involved inthe metastatic cascade. It is likely that in some cases the augmentedmetastatic potential of certain tumour cells may be due to an increasedexpression of oncogenes, which normally are responsible for control ofvarious cellular functions, including differentiation, proliferation,cell motility, and communication. Further, it has been shown thatsubstances that modulate signal transduction pathways can inhibit themetastatic behaviour of a tumour, and it is also speculated thatcompounds with surface related effects, e.g. compounds which modulatesthe cell membranes, might be involved in the process leading tometastasis.

[0011] Cancer is a disease of inappropriate tissue accumulation. Thisderangement is most evident clinically when tumour tissue bulkcompromises the function of vital organs. Contrary to what is generallythought, human malignant disorders are usually not diseases of rapidcell proliferation. In fact, the cells of most common cancersproliferate more slowly than many cells in normal tissues. It is arelatively slow accumulation of tumour tissue within vital organs thatproves fatal to most patients who die of cancer.

[0012] Chemotherapeutic agents share one characteristic: they areusually more effective in killing or damaging malignant cells thannormal cells. However, the fact that they do harm normal cells indicatestheir potential for toxicity.

[0013] Nearly all chemotherapeutic agents currently in use interferewith DNA synthesis, with the provision of precursors for DNA and RNAsynthesis, or with mitosis. Such drugs are most effective againstcycling cells. The mechanism of cell death after treatment with anysingle agent or combination of agents is complex and is likely toinclude more than one process. Because most clinically detectabletumours are composed mostly of non-cycling cells, it is not surprisingthat chemotherapy is not always effective in eradicating cancer.

[0014] The strategy of cancer treatment is to shift tumour cells from anon-cycling compartment to a cycling compartment. Several methods thatpromote this shift form the basis for combined-modality treatment.Surgery is most commonly used to reduce tumour size and thus facilitatere-entry of cancer cells into the cell cycle. After the primary tumouris completely removed, microscopic metastases may remain at distantsites. Because of their small size, the micrometastases are composedprincipally of cycling cells. Small numbers of cells that remain atprimary tumour site are also likely to re-enter the cell cycle. Thus,the remaining cancer cells are often susceptible to chemotherapy.Radiation therapy or chemotherapy alone can also be used to reducetumour bulk and thus recruit cells into the cycling cell compartment.

[0015] Combination drug therapy is, therefore, the basis for mostchemotherapy employed at present. Combination chemotherapy uses thedifferent mechanisms of action and cytotoxic potentials of multipledrugs.

[0016] However, even though the chemotherapeutic agents are moreeffective in killing or damaging malignant cells than normal cells, thefact that they do harm normal cells indicates their great potential fortoxicity. For chemotherapy to be effective, the patient must be in goodphysiologic condition.

[0017] Cancer treatment requires inhibition of a variety of factorsincluding tumour cell proliferation, metastatic dissemination of cancercells to other parts of the body, invasion, tumour-inducedneovascularization, and enhancement of host immunological responses andcytotoxity. Conventional cancer chemotherapeutic agents have often beenselected on the basis of their cytotoxicity to tumour cells. However,some anticancer agents have adverse effects on the patient'simmunological system. Unfortunately, for the vast majority ofconventional antineoplastic agents the margin between an effective doseand a toxic dose, i.e., the therapeutic index, is extremely low. Thus,it would be greatly advantageous if a cancer therapy or treatment couldbe developed that would afford noncytotoxic protection against factorsthat might lead to growth, progression and metastasis of invasivecancers.

[0018] The present invention is directed to a method for the preventionand/or treatment of primary and metastatic neoplasms that involves usinga fatty acid analogues of the present invention to treat a patientsuffering from a cancer.

[0019] The two essential features of cancer are invasion and metastasis.At one extreme, microinvasion of the basement membrane characterises thetransition from neoplasia to cancer, and at the other extreme,metastases generally lead to death.

[0020] Invasion into the underlying connective tissue by primary tumourproceeds in stages and is facilitated by various mediators produced bythe tumour cells. Tumour cells that have not invaded the basementmembrane and remain confined within the epithelium are termed carcinomain situ.

[0021] Metastases, on the other hand, may form when circulating tumourcells with adherent lymphocytes and platelets are trapped in capillariesand the tumour cell membrane interacts with the capillary endothelium.The capillary endothelial junctions retract, and tumour cell ligandsbind to receptors on the endothelial and basement membranes. Tumourcells then release collagenase IV, which destroys collagen IV, a majorcomponent of the underlying basement membrane. Invasion of thesubcapillary connective tissue is aided by binding to the glycoproteinslaminin and fibronectin, by the release of proteases that destroy thematrix, and by the secretion of motility and chemotactic factors. Tumourcells then may proliferate and synthesise platelet aggregatory factorssuch as thromboxanes and procoagulants, thereby leading to thedeposition of a fibrin cocoon around the cells. Such a cocoon mayprotect the micrometastasis from attack by the host's immune system.

[0022] Cancers that can be prevented and/or treated by the compositionsand methods of the present invention include, but are not limited to,human sarcomas and carcinomas, e.g. carcinomas, e.g., colon carcinoma,pancreatic cancer, breast cancer, ovarian cancer, prostate cancer,fibrosarcoma, myxosarcoma, liposarcoma, chondrosarcoma, osteogenicsarcoma, chordoma, angiosarcoma, endothelio-sarcoma, lymphangiosarcoma,lymphangioendotheliosarcoma, synovioma, mesothelioma, Ewing's tumour,leiomyosarcoma, rhabdomyosarcoma, squamous cell carcinoma, basal cellcarcinoma, adenocarcinoma, sweat gland carcinoma, sebaceous glandcarcinoma, papillary carcinoma, papillary adenocarcinomas,cystadenocarcinoma, medullary carcinoma, bronchogenic carcinoma, renalcell carcinoma, hepatoma, bile duct carcinoma, choriocarcinoma,seminoma, embryonal carcinoma, Wilms' tumour, cervical cancer,testicular tumor, lung carcinoma, small cell lung carcinoma, bladdercarcinoma, epithelial carcinoma, glioma, astrocytoma, medulloblastoma,craniopharyngioma, ependymoma, pinealoma, hemangioblastoma, acousticneuroma, oligodendroglioma, meningioma, melanoma, neuroblastoma,retinoblastoma; leukemias, e.g., acute lymphocytic leukemia and acutemyelocytic leukemia (myeloblastic, promyelocytic, myelomonocytic,monocytic and erythroleukemia); chronic leukemia (chronic myelocytic(granulocytic) leukemia and chronic lymphocytic leukemia); andpolycythemia vera, lymphoma (Hodgkin's disease and non-Hodgkin'sdisease), multiple myeloma, Waldenstrom's macroglobulinemia, and heavychain disease. Specific examples of such cancers are described in thesections below

[0023] We have shown that the compound of the present inventiondecreases the average diameter of various spheroids and that the tumourvolume of BT4Cn tumours decreases. Further, we have shown that theoverall survival of TTA treated rats with implanted tumours issubstantially increased.

[0024] Thus, the fatty acid analogues of the present invention have beenproved to have a marked effect on the growth, invasion and metastasis oftumours.

[0025] Tetradecylthioacetic acid (TTA) is most thoroughly studiedcompound of the present invention, and we have shown several beneficialeffects in various in vitro and in vivo test systems.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention discloses that modified fatty acidanalogues at non-cytotoxic concentrations can be used for the treatmentand/or prevention of cancer.

[0027] The present invention relates to the use of fatty acid analoguesof the general formula (I):

R₁-[x_(i)-CH₂]_(n)—COOR₂   (I)

[0028] wherein R₁ is;

[0029] a C₁-C₂₄ alkene with one or more double bonds and/or with one ormore triple bonds, and/or

[0030] a C₁-C₂₄ alkyne, and/or

[0031] a C₁-C₂₄ alkyl, or an alkyl substituted in one or severalpositions with one or more compounds selected from the group comprisingfluoride, chloride, hydroxy, C₁-C₄ alkoxy, C₁-C₄ alkylthio,C₂-C₅-acyloxy or C₁-C₄ alkyl, and

[0032] wherein R₂ represents hydrogen or C₁-C₄ alkyl, and

[0033] wherein n is an integer from 1 to 12, and

[0034] wherein i is an odd number and indicates the position relative toCOOR₂, and

[0035] wherein X_(i) independent of each other are selected from thegroup comprising O, S, SO, SO₂, Se and CH₂, and

[0036] with the proviso that at least one of the X_(i) is not CH₂,

[0037] or a salt, prodrug and complex thereof, for the preparation of apharmaceutical composition for the treatment and/or inhibition ofprimary and secondary metastatic neoplasms.

[0038] Presently preferred embodiments of the present invention relatesto the compounds tetradecylthioacetic acid (TTA) andtetradecylselenioacetic acid (TSA).

[0039] More specifically, the invention relates to the use of thecompounds for the inhibition of the growth, invasive and metastaticproperties of tumours.

[0040] A further aspect of the invention relates to a method for thetreatment and/or inhibition of primary and secondary metastaticneoplasms, said method comprising the step of administering to a mammalin need thereof an effective amount of fatty acid analogues of thegeneral formula (I):

R₁-[x_(i)-CH₂]_(n)—COOR₂   (I)

[0041] wherein R₁ is:

[0042] a C₁-C₂₄ alkene with one or more double bonds and/or with one ormore triple bonds, and/or

[0043] a C₁-C₂₄ alkyne, and/or

[0044] a C₁-C₂₄ alkyl, or an alkyl substituted in one or severalpositions with one or more compounds selected from the group comprisingfluoride, chloride, hydroxy, C₁-C₄ alkoxy, C₁-C₄ alkylthio, C₂-C₅acyloxy or C₁-C₄ alkyl, and

[0045] wherein R2 represents hydrogen or C₁-C₄ alkyl, and

[0046] wherein n is an integer from 1 to 12, and

[0047] wherein i is an odd number and indicates the position relative toCOOR₂, and

[0048] wherein X_(i) independent of each other are selected from thegroup comprising O, S, SO, SO₂, Se and CH₂, and

[0049] with the proviso that at least one of the X_(i) is not CH₂,

[0050] or a salt, prodrug and complex thereof.

[0051] The treatment involves administering to a mammal in need of suchtreatment a therapeutically effective concentration which is maintainedsubstantially continuously in the blood of the animal for the durationof the period of its administration.

FIGURE LEGENDS

[0052]FIG. 1 shows the effect of TTA on the spheroid diameter of D-54Mgspheroids.

[0053]FIG. 2 shows the effect of TTA on the spheroid diameter of GaMgspheroids.

[0054]FIG. 3 shows the effect of various concentrations of TTA on thespheroid diameter of D-54Mg spheroids.

[0055]FIG. 4 shows the effect of TTA on the growth of subcutaneouslyimplanted BT4Cn tumours.

[0056]FIG. 5 shows the effect of TTA on the survival of rats withintracranically implanted BT4Cn tumours.

ADMINISTRATION OF THE COMPOUNDS OF THE PRESENT INVENTION

[0057] As a pharmaceutical medicament the compounds of the presentinvention may be administered directly to the mammal by any suitabletechnique, including parenterally, intranasally, orally, or byabsorption through the skin. They can be administered locally orsystemically. The specific route of administration of each agent willdepend, e.g., on the medical history of the animal.

[0058] Examples of parenteral administration include subcutaneous,intramuscular, intravenous, intraarterial, and intraperitonealadministration.

[0059] As a general proposition, the total pharmaceutically effectiveamount of each of the compounds administered parenterally per dose willpreferably be in the range of about 5 mg/kg/day to 1000 mg/kg/day ofpatient body weight, although, as noted above, this will be subject to agreat deal of therapeutic discretion. For TTA it is expected that a doseof 100-500 mg/kg/day is preferable, and for TSA the dosage couldprobably in the range of from 10 to 100 mg/kg/day.

[0060] If given continuously, the compounds of the present invention areeach typically administered by 1-4 injections per day or by continuoussubcutaneous infusions, for example, using a mini-pump. An intravenousbag solution may also be employed.

[0061] For parenteral administration, in one embodiment, the compoundsof the present invention are formulated generally by mixing each at thedesired degree of purity, in a unit dosage injectable form (solution,suspension, or emulsion), with a pharmaceutically acceptable carrier,i.e., one that is non-toxic to recipients at the dosages andconcentrations employed and is compatible with other ingredients of theformulation.

[0062] Generally, the formulations are prepared by contacting thecompounds of the present invention each uniformly and intimately withliquid carriers or finely divided solid carriers or both. Then, ifnecessary, the product is shaped into the desired formulation.Preferably the carrier is a parenteral carrier, more preferably asolution that is isotonic with the blood of the recipient. Examples ofsuch carrier vehicles include water, saline, Ringer's solution, anddextrose solution. Non-aqueous vehicles such as fixed oils and ethyloleate are also useful herein, as well as liposomes.

[0063] The carrier may suitably contain minor amounts of additives suchas substances that enhance isotonicity and chemical stability. Suchmaterials are non-toxic to recipients at the dosages and concentrationsemployed, and include buffers such as phosphate, citrate, succinate,acetic acid, and other organic acids or their salts; antioxidants suchas ascorbic acid; immunoglobulins; hydrophilic polymers such aspolyvinylpyrrolidone; amino acids, such as glycine, glutamic acid,aspartic acid, or arginine; monosaccharides, disaccharides, and othercarbohydrates including cellulose or its derivatives, glucose, mannose,or dextrins; chelating agents such as EDT'A sugar alcohols such asmannitol or sorbitol; counterions such as sodium; and/or non-ionicsurfactants such as polysorbates, poloxamers, or PEG.

[0064] For oral pharmacological compositions such carrier material as,for example, water, gelatine, gums, lactose, starches,magnesium-stearate, talc, oils, polyalkene glycol, petroleum jelly andthe like may be used. Such pharmaceutical preparation may be in unitdosage form and may additionally contain other therapeutically valuablesubstances or conventional pharmaceutical adjuvants such aspreservatives, stabilising agents, emulsifiers, buffers and the like.The pharmaceutical preparations may be in conventional liquid forms suchas tablets, capsules, dragees, ampoules and the like, in conventionaldosage forms, such as dry ampoules, and as suppositories and the like.

[0065] In addition, the compounds of the present invention areappropriately administered in combination with other treatments forcombating or preventing cancer.

[0066] The invention will be more fully understood by reference to thefollowing examples. They should not, however, be construed as limitingthe scope of the invention.

EXPERIMENTAL SECTION EXAMPLE 1

[0067] Preparation and Characterisation of the Compounds

[0068] The Synthesis of 3-Substituted Fatty Acid Analogues

[0069] The compounds used according to the present invention wherein thesubstituent x_(i=3) is a sulphur atom or selenium atom may be preparedaccording to the following general procedure:

[0070] X is a Sulphur Atom:

[0071] The thio-substituted compound used according to the presentinvention may be prepared by the general procedure indicated below:

[0072] The sulphur-compound, namely, tetradecylthioaceticacid (TTA),(CH₃—(CH₂)₁₃—S—CH₂—COOH was prepared as shown in EP-345.038.

[0073] X is a Selenium Atom:

[0074] the seleno-substituted compound used according to the presentinvention may be prepared by the following general procedure

[0075] 1. Alkyl-Hal+KSeCN

Alkyl-SeCN . . .

[0076] 2. Alkyl-SeCN+BH₄ ⁻

Alkyl-Se⁻

[0077] 3. Alkyl-Se⁻+O₂

Alkyl-Se-Se-Alkyl

[0078] This compound was purified by carefully crystallisation fromethanol or methanol.

[0079] 5. Alkyl-Se⁻+Hal-CH²⁻COOH

Alkyl-Se-CH₂—COOH

[0080] The final compound, e.g. when alkyl is tetradecyl,(CH₃—(CH₂)₁₃—Se—CH₂—COOH (tetradecylselinioacetic acid (TSA)) can bepurified by crystallisation from diethyl ether and hexane.

[0081] Other compounds in accordance with the present invention can besynthesised as indicated in applicant patent applications PCT/NO99/00135and NO 20001123.

EXAMPLE 2

[0082] Toxicity Study of TTA

[0083] A 28 days toxicity study in dogs according to GLP guidelines hasbeen performed by Corning Hazleton (Europe), England. Oraladministration of TTA at dose levels up to 500 mg/kg/day was generallywell tolerated. Some lipid related parameters were lowered in theanimals given high dosages. This is consistent with the pharmacologicalactivity of TTA. There was no evidence of toxicity at dose levels of 50or 500 mg/day/kg.

[0084] Covance Laboratories Limited, England, has performed tests formutagenic activity. It was concluded that TTA and TSA did not inducemutations in strains of Salmonella typhimurium and Escherichia coli.Furthermore, TTA was not mutagenic when tested in mouse lymphoma cellsand L5178Y.

[0085] The concentration of the compounds tested in S. typhimurium andE. coli were 3-1000 mg/plate (TTA) 2-5000 mg/plate (TSA). In mouselymphoma cells, L5178Y, the concentration was 2.5-50 mg/ml.

[0086] TSA and TSA were found not to be mutagenic in these tests. TSAand TTA have been tested for chromosomal aberrations in cultured Chinesehamster ovary cells and no aberrations were induced by the doses tested(12-140 mg/ml).

[0087] The compounds of the present invention are therefore potentiallyuseful as pharmaceutical compounds in this respect.

EXAMPLE 3

[0088] The Effect TTA on the Spheroid Growth.

[0089] Multicellular tumour spheroids were obtained by seeding 3×10⁶cells into 80 cm² tissue culture flasks base coated with a 10 ml(KB/KJT=20 ml) 0.75% -agar DMEM solution (KB/KJT-30). After 7 daysincubation, spheroids with diameters between 100 and 300 μm wereselected with a Pasteur pipette under a stereomicroscope. The spheroidsize was determined by using an inverted microscope with a calibratedreticule in the eyepiece.

[0090] To compare the effect of the different fatty acid analogues ontumuor spheroid growth, both D-54Mg and GaMg spheroids were transferredindividually into 16 mm 24-well dishes base coated with 0.5 ml 0.75%DMEM-agar. D-54Mg and GaMg are human cell lines. The D-54Mg cell linewas derived from a mixed anaplastic glioma and was kindly supplied byDr. Darell D. Biqner, Duke University, Durham, N.C. The GaMg cell linewas established in our laboratory and has been described in detailelsewhere (Bjerkvik et al. Anticancer research 1998: vol 8, p 797-803).The spheroids were divided into 5 groups with 4 spheroids in each group.Four groups were treated with the different fatty acid analogues at afinal fatty acid concentration of either 100 or 250 μM. The fifth group(control) did not receive any treatment. The volume of the overlaysuspension was 1.0 ml. The size of the spheroids were determined everysecond day be measured two orthogonal diameters using an inverted phasecontrast microscope with a calibrated reticle in the eye-piece. This wasdone during a 14-day period.

[0091] The results of these experiments are shown in FIGS. 1-3. Asindicated, the fatty acids were exposed to the spheroids during a 14 daylong period. No fatty acids were supplemented to the control group (

). The values are presented as mean ±SD.

[0092]FIG. 1 shows the effect of 250 μM TTA (

) and PA (

) on the average spheroid diameter (μm) of D-54Mg spheroids.

[0093]FIG. 2 shows the effect of 250 μM TTA (

) and PA (

) on the average spheroid diameter (μm) of GaMg spheroids.

[0094] To study the dose dependent effect of TTA on spheroid growth, 24tumour spheroids from both cell lines were divided into 6 groups whichreceived 0, 50, 100, 150, 200 and 250 μM of TTA. This experiment wasperformed in SF-X medium (available from Costar, Mass, USA), and theresults are given in FIG. 3.

EXAMPLE 4

[0095] Cell Migration.

[0096] The effect of the fatty acid analogues on cell migration wasstudied by measuring the ability of cells to migrate out from spheroidsthat had attached to a plastic surface. GaMg and D-54Mg spheroids withdiameters between 200 and 300 μm were transferred individually into 16mm 24-well dishes. 1.5 ml of DMEM was then added with variousconcentrations of the different fatty acid analogues. After 3 days ofculture the specimens were fixed with 4% formaldehyde on PBS and stainedwith 2% crystal violet in 96% ethanol. The size of the outgrowth areawas then determined by using a Kontron morphometry system (Kontron,Eching, Germany). We used a serum supplemented medium (DMEM) in thisassay due to a relative loose attachment of glioma cells to the plasticsurface in the SF-X medium. The migratory capacity of the GaMg andD-54MG cells were severely inhibited by TTA at a concentration of 100 μM(data not shown).

EXAMPLE 5

[0097] The Effect of TTA on the Growth of Subcutaneously Implanted BT4CnTumours.

[0098] Mail Norwegian brown rats, BD IX, were obtained from GadesInstitute, Haukeland hospital, Bergen, Norway. They were housed incages, in pairs, and maintained on a 12 h cycle light and dark at atemperature of 20±3° C. During the experiments they weighted 250-400 g.They were fed a commercial standard pelleted food and provided tap waterad libitum. Test groups were treated with TTA, and control groupstreated with palmitate and/or carboxymethyl cellulose (CMC).

[0099] The TTA was administered by oro-gastric intubation. TTA and PAwere suspended in 0.5% (w/v) sodium carboxymethyl cellulose at a finalstock solution of 75 mg/ml. The animals were administered once a day ata dose of 300 mg/kg body weight.

[0100] The rats were anaesthetised with 0,2 ml Hypnorm-Dormicum/100 gbody weight and a tumour was established in vivo, by subcutanouslyinjection of 5*10⁶ tumour cells (in 1 ml NaCl) in the rat's neck. After3-4 weeks, the tumour was removed and cut into 2*2 mm tissue pieces. Thepieces were used for establishment of s.c. tumours in the leg. The ratswere anaesthetised with 0.2 ml Hypnorm-Dormicum/100 g body weight, askin incision was made, and the tissue piece was entered and establishedapproximately 1 cm below the skin incision. The tumours were grown for 2weeks. The rats were treated either by oro-gastric intubation or bydirect injection in tumour.

[0101] The volume of the tumours (at leg) were measured.

[0102]FIG. 4 shows the effect of PA (

) and TTA (

) on the growth of subcutaneously implanted BT4Cn tumours.

EXAMPLE 6

[0103] The Effect of TTA on the Survival of Rats With IntracranicallyImplanted BT4Cn Tumours.

[0104] Mail Norwegian brown rats, BD IX, were used as described inexample 5. The TTA was administered by oro-gastric intubation.

[0105] The tumour was implanted by stereotactical transplantation. Therate were anaesthetised with 0.4 ml Equithesin/100 g body weight. A skinincision was made, blood was removed by H₂O₂ and the scull was trephinedusing a dental drill.

[0106] The burr hole was localized 3.3 mm posterior to the coronalsuture and 2.5 mm lateral to the sagittal suture.

[0107] Cells were harvested and counted as described above (Section5.3), and then diluted in DPBS to a final concentration on 20.000cells/μl. 2 μl cell suspension was injected with a Hamilton syringe witha cone-tipped 0.7 mm needle at a depth of 2.8 mm. The skin was closedwith steel staples, and the animals were returned to their cages.

[0108]FIG. 5 shows the effect of PA and TTA on the survival of rats withintracranially implanted BT4Cn tumours.

1. Use of fatty acid analogues of the general formula (I):R₁-[x_(i)-CH₂]_(n)—COOR₂   (I) wherein R₁ is; a C₁-C₂₄ alkene with oneor more double bonds and/or with one or more triple bonds, and/or aC₁-C₂₄ alkyne, and/or a C₁-C₂₄ alkyl, or an alkyl substituted in one orseveral positions with one or more compounds selected from the groupcomprising fluoride, chloride, hydroxy, C₁-C₄ alkoxy, C₁-C₄ alkylthio,C₂-C₅ acyloxy or C₁-C₄ alkyl, and wherein R2 represents hydrogen orC₁-C₄ alkyl, and wherein n is an integer from 1 to 12, and wherein i isan odd number and indicates the position relative to COOR₂, and whereinX_(i) independent of each other are selected from the group comprisingO, S, SO, SO₂, Se and CH₂, and with the proviso that at least one of theX_(i) is not CH₂ or a salt, prodrug or complex thereof, for thepreparation of a pharmaceutical composition for the prevention and/orinhibition of primary and secondary neoplasms.
 2. The use according toclaim 1, wherein the compound is tetradecylthioacetic acid.
 3. The useaccording to claim 1, wherein the compounds is tetradecylselenoaceticacid.
 4. The use according to claim 1 for the inhibition of the growthof tumours.
 5. The use according to claim 1 for the inhibition of theinvasion of a primary tumour into the connective tissue.
 6. The useaccording to claim 1 for the inhibition of the metastatic properties ofa tumour, i.e. to inhibit the formation of secondary tumours.
 7. The useaccording to claim 1, for increasing the overall survival of mammalswith tumours.
 8. A method for the treatment and/or inhibition of primaryand secondary metastatic neoplasms, said method comprising the step ofadministering to a mammal in need thereof an effective amount of fattyacid analogues of the general formula (I): R₁-[x_(i)-CH₂]_(n)—COOR₂  (I) wherein R₁ is; a C₁-C₂₄ alkene with one or more double bondsand/or with one or more triple bonds, and/or a C₁-C₂₄ alkyne, and/or aC₁-C₂₄ alkyl, or an alkyl substituted in one or several positions withone or more compounds selected from the group comprising fluoride,chloride, hydroxy, C₁-C₄ alkoxy, C₁-C₄ alkylthio, C₂-C₅ acyloxy or C₁-C₄alkyl, and wherein R2 represents hydrogen or C₁-C₄ alkyl, and wherein nis an integer from 1 to 12, and wherein i is an odd number and indicatesthe position relative to COOR₂, and wherein x_(i) independent of eachother are selected from the group comprising O, S, SO, SO₂, Se and CH₂,and with the proviso that at least one of the x_(i) is not CH_(2,) or asalt, prodrug or complex thereof.
 9. The method according to claim 8,wherein the compound is tetradecylthioacetic acid.
 10. The methodaccording to claim 8, wherein the compounds is tetradecylselenoaceticacid.
 11. A method in accordance with one of previous claims, whereinthe fatty acid analogues are administrated such that its therapeuticallyeffective concentration is maintained substantially continuously in theblood of the mammal for the duration of the period of itsadministration.
 12. A method in accordance with one of the previousclaims, wherein the composition of said fatty acid analogues compositionis in unit dosage forms.